Production line module for forming multiple sized photovoltaic devices

ABSTRACT

The present invention generally relates to a sectioning module positioned within an automated solar cell device fabrication system. The solar cell device fabrication system is adapted to receive a single large substrate and form multiple silicon thin film solar cell devices from the single large substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Patent ApplicationSer. No. 60/967,077, filed Aug. 31, 2007 (Attorney Docket No.APPM/011141 L), U.S. Provisional Patent Application Ser. No. 61/023,214,filed Jan. 24, 2008 (Attorney Docket No. APPM/12959L), U.S. ProvisionalPatent Application Ser. No. 61/034,931, filed Mar. 7, 2008 (AttorneyDocket No. APPM/12959L02), U.S. Provisional Patent Application Ser. No.61/023,739, filed Jan. 25, 2008 (Attorney Docket No. APPM/12960L), U.S.Provisional Patent Application Ser. No. 61/023,810, filed Jan. 25, 2008(Attorney Docket No. APPM/12961L), U.S. Provisional Patent ApplicationSer. No. 61/020,304, filed Jan. 10, 2008 (Attorney Docket No.APPM/12962L), U.S. Provisional Patent Application Ser. No. 61/032,005,filed Feb. 27, 2008 (Attorney Docket No. APPM/13160), U.S. ProvisionalPatent Application Ser. No. 61/036,691, filed Mar. 14, 2008 (AttorneyDocket No. APPM/13177L02), U.S. Provisional Patent Application Ser. No.61/043,060, filed Apr. 8, 2008 (Attorney Docket No. APPM/13321L), andU.S. Provisional Patent Application Ser. No. 61/044,852, filed Apr. 14,2008 (Attorney Docket No. APPM/13322L), which are all incorporated byreference in their entireties.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention generally relate to a module of aproduction line used to form multiple sized solar cell devices.

2. Description of the Related Art

Photovoltaic (PV) devices or solar cells are devices which convertsunlight into direct current (DC) electrical power. Typical thin filmtype PV devices, or thin film solar cells, have one or more p-i-njunctions. Each p-i-n junction comprises a p-type layer, an intrinsictype layer, and an n-type layer. When the p-i-n junction of the solarcell is exposed to sunlight (consisting of energy from photons), thesunlight is converted to electricity through the PV effect. Solar cellsmay be tiled into larger solar arrays. The solar arrays are created byconnecting a number of solar cells and joining them into panels withspecific frames and connectors.

Typically, a thin film solar cell includes active regions, orphotoelectric conversion units, and a transparent conductive oxide (TCO)film disposed as a front electrode and/or as a back electrode. Thephotoelectric conversion unit includes a p-type silicon layer, an n-typesilicon layer, and an intrinsic type (i-type) silicon layer sandwichedbetween the p-type and n-type silicon layers. Several types of siliconfilms including microcrystalline silicon film (μc-Si), amorphous siliconfilm (a-Si), polycrystalline silicon film (poly-Si), and the like may beutilized to form the p-type, n-type, and/or i-type layers of thephotoelectric conversion unit. The backside electrode may contain one ormore conductive layers. There is a need for an improved process offorming a solar cell that has good interfacial contact, low contactresistance and provides a high overall electrical device performance.

With traditional energy source prices on the rise, there is a need for alow cost way of producing electricity using a low cost solar celldevice. Conventional solar cell manufacturing processes are highly laborintensive and have numerous interruptions that can affect the productionline throughput, solar cell cost, and device yield. For instance,particular solar cell device sizes are needed for particularapplications. Conventional solar cell lines are either capable ofproducing only a single sized solar cell device or require significantdowntime to manually convert the solar cell production line processes toaccommodate a different substrate size and produce a different sizedsolar cell device. Thus, there is a need for a production line that isable to perform all phases of the fabrication process for producingmultiple sized solar cell devices from a single large substrate.

SUMMARY OF THE INVENTION

In one embodiment of the present invention, a module for sectioning asolar cell device comprises an inlet conveyor configured to receivecommands from a system controller and transfer a solar cell device intoa scribing station of the module, a scribing mechanism configured toreceive commands from the system controller and scribe a pattern into afirst surface of the solar cell device, a first positioning mechanismconfigured to receive commands from the system controller and accuratelyposition the scribed solar cell device over a first break mechanism, anda first actuator configured to receive commands from the systemcontroller and raise the first break mechanism.

In another embodiment of the present invention, a method for sectioninga partially processed solar cell device comprises receiving a substratehaving a processing surface, forming a silicon layer on the processingsurface, sectioning the substrate into a first and second section afterforming the silicon layer on the processing surface, and transferringthe first section into a next station for further processing.

In another embodiment of the present invention, a system for fabricatingsolar cell devices comprises a substrate receiving module that isadapted to receive a substrate, a cluster tool having a processingchamber that is adapted to deposit a silicon-containing layer on asurface of the substrate, a back contact deposition chamber configuredto deposit a back contact layer on a surface of the substrate, asubstrate sectioning module configured to section the substrate into twoor more sections, and a system controller for controlling andcoordinating functions of each of the substrate receiving module, thecluster tool, the processing chamber, the back contact depositionchamber, and the substrate sectioning module.

In yet another embodiment of the present invention, a method ofprocessing a solar cell device comprises cleaning a substrate to removeone or more contaminants from a surface of the substrate, depositing aphotoabsorbing layer on the surface of the substrate, removing at leasta portion of the photoabsorbing layer from a region on a surface of thesubstrate, depositing a back contact layer on the surface of thesubstrate, sectioning the substrate into two or more sections,performing an edge deletion process on a surface of one of the sectionsbonding a back glass substrate to the surface of one of the sections toform a composite structure, and attaching a junction box to thecomposite structure.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 illustrates a process sequence for forming a solar cell deviceaccording to one embodiment described herein.

FIG. 2 illustrates a plan view of a solar cell production line accordingto one embodiment described herein.

FIG. 3A is a side cross-sectional view of a thin film solar cell deviceaccording to one embodiment described herein.

FIG. 3B is a side cross-sectional view of a thin film solar cell deviceaccording to one embodiment described herein.

FIG. 3C is a plan view of a composite solar cell structure according toone embodiment described herein.

FIG. 3D is a cross-sectional view of along Section A-A of FIG. 3C.

FIG. 3E is a side cross-sectional view of a thin film solar cell deviceaccording to one embodiment described herein.

FIGS. 4A-4E are schematic plan views illustrating the sequencing of asectioning module according to one embodiment of the present invention.

FIGS. 5A-5C are schematic side views of portions of the sectioningmodule illustrating a sequence of sectioning a substrate according toone embodiment of the present invention.

DETAILED DESCRIPTION

Embodiments of the present invention generally relate to a system usedto form solar cell devices using processing modules adapted to performone or more processes in the formation of the solar cell devices. In oneembodiment, the system is adapted to form thin film solar cell devicesby accepting a large unprocessed substrate and performing multipledeposition, material removal, cleaning, sectioning, bonding, and testingprocesses to form multiple complete, functional, and tested solar celldevices that can then be shipped to an end user for installation in adesired location to generate electricity. In one embodiment, the systemis capable of accepting a single large unprocessed substrate andproducing multiple smaller solar cell devices. In one embodiment, thesystem is capable of changing the sizes of the solar cell devicesproduced from the single large substrate without manually moving oraltering any of the system modules. While the discussion below primarilydescribes the formation of silicon thin film solar cell devices, thisconfiguration is not intended to be limiting as to the scope of theinvention since the apparatus and methods disclosed herein can also beused to form, test, and analyze other types of solar cell devices, suchas III-V type solar cells, thin film chalcogenide solar cells (e.g.,CIGS, CdTe cells), amorphous or nanocrystalline silicon solar cells,photochemical type solar cells (e.g., dye sensitized), crystallinesilicon solar cells, organic type solar cells, or other similar solarcell devices.

The system is generally an arrangement of automated processing modulesand automation equipment used to form solar cell devices that areinterconnected by an automated material handling system. In oneembodiment, the system is a fully automated solar cell device productionline that is designed to reduce and/or remove the need for humaninteraction and/or labor intensive processing steps to improve thedevice reliability, process repeatability, and the cost of ownership ofthe formation process. In one configuration, the system is adapted toform multiple silicon thin film solar cell devices from a single largesubstrate and generally comprises a substrate receiving module that isadapted to accept an incoming substrate, one or more absorbing layerdeposition cluster tools having at least one processing chamber that isadapted to deposit a silicon-containing layer on a processing surface ofthe substrate, one or more back contact deposition chambers that isadapted to deposit a back contact layer on the processing surface of thesubstrate, one or more material removal chambers that are adapted toremove material from the processing surface of each substrate, one ormore sectioning modules used to section the processed substrate intomultiple smaller processed substrates, a solar cell encapsulationdevice, an autoclave module that is adapted to heat and expose acomposite solar cell structure to a pressure greater than atmosphericpressure, a junction box attaching region to attach a connection elementthat allows the solar cells to be connected to external components, andone or more quality assurance modules adapted to test and qualify eachcompletely formed solar cell device. The one or more quality assurancemodules generally include a solar simulator, a parametric testingmodule, and a shunt bust and qualification module.

FIG. 1 illustrates one embodiment of a process sequence 100 thatcontains a plurality of steps (i.e., steps 102-142) that are each usedto form a solar cell device using a novel solar cell production line 200described herein. The configuration, number of processing steps, andorder of the processing steps in the process sequence 100 is notintended to be limiting to the scope of the invention described herein.FIG. 2 is a plan view of one embodiment of the production line 200,which is intended to illustrate some of the typical processing modulesand process flows through the system and other related aspects of thesystem design, and is thus not intended to be limiting to the scope ofthe invention described herein.

In general, a system controller 290 may be used to control one or morecomponents found in the solar cell production line 200. The systemcontroller 290 is generally designed to facilitate the control andautomation of the overall solar cell production line 200 and typicallyincludes a central processing unit (CPU) (not shown), memory (notshown), and support circuits (or I/O) (not shown). The CPU may be one ofany form of computer processors that are used in industrial settings forcontrolling various system functions, substrate movement, chamberprocesses, and support hardware (e.g., sensors, robots, motors, lamps,etc.), and monitor the processes (e.g., substrate support temperature,power supply variables, chamber process time, I/O signals, etc.). Thememory is connected to the CPU, and may be one or more of a readilyavailable memory, such as random access memory (RAM), read only memory(ROM), floppy disk, hard disk, or any other form of digital storage,local or remote. Software instructions and data can be coded and storedwithin the memory for instructing the CPU. The support circuits are alsoconnected to the CPU for supporting the processor in a conventionalmanner. The support circuits may include cache, power supplies, clockcircuits, input/output circuitry, subsystems, and the like. A program(or computer instructions) readable by the system controller 290determines which tasks are performable on a substrate. Preferably, theprogram is software readable by the system controller 290 that includescode to perform tasks relating to monitoring, execution and control ofthe movement, support, and/or positioning of a substrate along with thevarious process recipe tasks and various chamber process recipe stepsbeing performed in the solar cell production line 200. In oneembodiment, the system controller 290 also contains a plurality ofprogrammable logic controllers (PLC's) that are used to locally controlone or more modules in the solar cell production, and a materialhandling system controller (e.g., PLC or standard computer) that dealswith the higher level strategic movement, scheduling and running of thecomplete solar cell production line. An example of a system controller,distributed control architecture, and other system control structurethat may be useful for one or more of the embodiments described hereincan be found in the U.S. Provisional Patent Application Ser. No.60/967,077, which has been incorporated by reference.

Examples of a solar cell 300 that can be formed using the processsequence(s) illustrated in FIG. 1 and the components illustrated in thesolar cell production line 200 are illustrated in FIGS. 3A-3E. FIG. 3Ais a simplified schematic diagram of a single junction amorphous ormicro-crystalline silicon solar cell 300 that can be formed and analyzedin the system described below. As shown in FIG. 3A, the single junctionamorphous or micro-crystalline silicon solar cell 300 is oriented towarda light source or solar radiation 301. The solar cell 300 generallycomprises a substrate 302, such as a glass substrate, polymer substrate,metal substrate, or other suitable substrate, with thin films formedthereover. In one embodiment, the substrate 302 is a glass substratethat is about 2200 mm×2600 mm×3 mm in size. The solar cell 300 furthercomprises a first transparent conducting oxide (TCO) layer 310 (e.g.,zinc oxide (ZnO), tin oxide (SnO)) formed over the substrate 302, afirst p-i-n junction 320 formed over the first TCO layer 310, a secondTCO layer 340 formed over the first p-i-n junction 320, and a backcontact layer 350 formed over the second TCO layer 340. To improve lightabsorption by enhancing light trapping, the substrate and/or one or moreof the thin films formed thereover may be optionally textured by wet,plasma, ion, and/or mechanical processes. For example, in the embodimentshown in FIG. 3A, the first TCO layer 310 is textured, and thesubsequent thin films deposited thereover generally follow thetopography of the surface below it. In one configuration, the firstp-i-n junction 320 may comprise a p-type amorphous silicon layer 322, anintrinsic type amorphous silicon layer 324 formed over the p-typeamorphous silicon layer 322, and an n-type microcrystalline siliconlayer 326 formed over the intrinsic type amorphous silicon layer 324. Inone example, the p-type amorphous silicon layer 322 may be formed to athickness between about 60 Å and about 300 Å, the intrinsic typeamorphous silicon layer 324 may be formed to a thickness between about1,500 Å and about 3,500 Å, and the n-type microcrystalline semiconductorlayer 326 may be formed to a thickness between about 100 Å and about 400Å. The back contact layer 350 may include, but is not limited to amaterial selected from the group consisting of Al, Ag, Ti, Cr, Au, Cu,Pt, alloys thereof, and combinations thereof.

FIG. 3B is a schematic diagram of an embodiment of a solar cell 300,which is a multi-junction solar cell that is oriented toward the lightor solar radiation 301. The solar cell 300 comprises a substrate 302,such as a glass substrate, polymer substrate, metal substrate, or othersuitable substrate, with thin films formed thereover. The solar cell 300may further comprise a first transparent conducting oxide (TCO) layer310 formed over the substrate 302, a first p-i-n junction 320 formedover the first TCO layer 310, a second p-i-n junction 330 formed overthe first p-i-n junction 320, a second TCO layer 340 formed over thesecond p-i-n junction 330, and a back contact layer 350 formed over thesecond TCO layer 340. In the embodiment shown in FIG. 3B, the first TCOlayer 310 is textured, and the subsequent thin films deposited thereovergenerally follow the topography of the surface below it. The first p-i-njunction 320 may comprise a p-type amorphous silicon layer 322, anintrinsic type amorphous silicon layer 324 formed over the p-typeamorphous silicon layer 322, and an n-type microcrystalline siliconlayer 326 formed over the intrinsic type amorphous silicon layer 324. Inone example, the p-type amorphous silicon layer 322 may be formed to athickness between about 60 Å and about 300 Å, the intrinsic typeamorphous silicon layer 324 may be formed to a thickness between about1,500 Å and about 3,500 Å, and the n-type microcrystalline semiconductorlayer 326 may be formed to a thickness between about 100 Å and about 400Å. The second p-i-n junction 330 may comprise a p-type microcrystallinesilicon layer 332, an intrinsic type microcrystalline silicon layer 334formed over the p-type microcrystalline silicon layer 332, and an n-typeamorphous silicon layer 336 formed over the intrinsic typemicrocrystalline silicon layer 334. In one example, the p-typemicrocrystalline silicon layer 332 may be formed to a thickness betweenabout 100 Å and about 400 Å, the intrinsic type microcrystalline siliconlayer 334 may be formed to a thickness between about 10,000 Å and about30,000 Å, and the n-type amorphous silicon layer 336 may be formed to athickness between about 100 Å and about 500 Å. The back contact layer350 may include, but is not limited to a material selected from thegroup consisting of Al, Ag, Ti, Cr, Au, Cu, Pt, alloys thereof, andcombinations thereof.

FIG. 3C is a plan view that schematically illustrates an example of therear surface of a formed solar cell 300 that has been produced in theproduction line 200. FIG. 3D is a side cross-sectional view of portionof the solar cell 300 illustrated in FIG. 3C (see section A-A). WhileFIG. 3D illustrates the cross-section of a single junction cell similarto the configuration described in FIG. 3A, this is not intended to belimiting as to the scope of the invention described herein.

As shown in FIGS. 3C and 3D, the solar cell 300 may contain a substrate302, the solar cell device elements (e.g., reference numerals 310-350),one or more internal electrical connections (e.g., side buss 355,cross-buss 356), a layer of bonding material 360, a back glass substrate361, and a junction box 370. The junction box 370 may generally containtwo connection points 371, 372 that are electrically connected toportions of the solar cell 300 through the side buss 355 and thecross-buss 356, which are in electrical communication with the backcontact layer 350 and active regions of the solar cell 300. To avoidconfusion relating to the actions specifically performed on thesubstrates 302 in the discussion below, a substrate 302 having one ormore of the deposited layers (e.g., reference numerals 310-350) and/orone or more internal electrical connections (e.g., side buss 355,cross-buss 356) disposed thereon is generally referred to as a devicesubstrate 303. Similarly, a device substrate 303 that has been bonded toa back glass substrate 361 using a bonding layer 360 is referred to as acomposite solar cell structure 304.

FIG. 3E is a schematic cross-section of a solar cell 300 illustratingvarious scribed regions used to form the individual cells 382A-382Bwithin the solar cell 300. As illustrated in FIG. 3E, the solar cell 300includes a transparent substrate 302, a first TCO layer 310, a firstp-i-n junction 320, and a back contact layer 350. Three laser scribingsteps may be performed to produce trenches 381A, 381B, and 381C, whichare generally required to form a high efficiency solar cell device.Although formed together on the substrate 302, the individual cells 382Aand 382B are isolated from each other by the insulating trench 381Cformed in the back contact layer 350 and the first p-i-n junction 320.In addition, the trench 381B is formed in the first p-i-n junction 320so that the back contact layer 350 is in electrical contact with thefirst TCO layer 310. In one embodiment, the insulating trench 381A isformed by the laser scribe removal of a portion of the first TCO layer310 prior to the deposition of the first p-i-n junction 320 and the backcontact layer 350. Similarly, in one embodiment, the trench 381B isformed in the first p-i-n junction 320 by the laser scribe removal of aportion of the first p-i-n junction 320 prior to the deposition of theback contact layer 350. While a single junction type solar cell isillustrated in FIG. 3E this configuration is not intended to be limitingto the scope of the invention described herein.

General Solar Cell Formation Process Sequence

Referring to FIGS. 1 and 2, the process sequence 100 generally starts atstep 102 in which a substrate 302 is loaded into the loading module 202found in the solar cell production line 200. In one embodiment, thesubstrates 302 are received in a “raw” state where the edges, overallsize, and/or cleanliness of the substrates 302 are not well controlled.Receiving “raw” substrates 302 reduces the cost to prepare and storesubstrates 302 prior to forming a solar device and thus reduces thesolar cell device cost, facilities costs, and production costs of thefinally formed solar cell device. However, typically, it is advantageousto receive “raw” substrates 302 that have a transparent conducting oxide(TCO) layer (e.g., first TCO layer 310) already deposited on a surfaceof the substrate 302 before it is received into the system in step 102.If a conductive layer, such as TCO layer, is not deposited on thesurface of the “raw” substrates then a front contact deposition step(step 107), which is discussed below, needs to be performed on a surfaceof the substrate 302.

In one embodiment, the substrates 302 or 303 are loaded into the solarcell production line 200 in a sequential fashion, and thus do not use acassette or batch style substrate loading system. A cassette styleand/or batch loading type system that requires the substrates to beun-loaded from the cassette, processed, and then returned to thecassette before moving to the next step in the process sequence can betime consuming and decrease the solar cell production line throughput.The use of batch processing does not facilitate certain embodiments ofthe present invention, such as fabricating multiple solar cell devicesfrom a single substrate. Additionally, the use of a batch style processsequence generally prevents the use of an asynchronous flow ofsubstrates through the production line, which is believed to provideimproved substrate throughput during steady state processing and whenone or more modules are brought down for maintenance or due to a faultcondition. Generally, batch or cassette based schemes are not able toachieve the throughput of the production line described herein, when oneor more processing modules are brought down for maintenance, or evenduring normal operation, since the queuing and loading of substrates canrequire a significant amount of overhead time.

In the next step, step 104, the surfaces of the substrate 302 areprepared to prevent yield issues later on in the process. In oneembodiment of step 104, the substrate is inserted into a front endsubstrate seaming module 204 that is used to prepare the edges of thesubstrate 302 or 303 to reduce the likelihood of damage, such aschipping or particle generation from occurring during the subsequentprocesses. Damage to the substrate 302 or 303 can affect device yieldand the cost to produce a usable solar cell device. In one embodiment,the front end seaming module 204 is used to round or bevel the edges ofthe substrate 302 or 303. In one embodiment, a diamond impregnated beltor disc is used to grind the material from the edges of the substrate302 or 303. In another embodiment, a grinding wheel, grit blasting, orlaser ablation technique is used to remove the material from the edgesof the substrate 302 or 303.

Next the substrate 302 or 303 is transported to the cleaning module 206,in which step 106, or a substrate cleaning step, is performed on thesubstrate 302 or 303 to remove any contaminants found on the surface ofthereof. Common contaminants may include materials deposited on thesubstrate 302 or 303 during the substrate forming process (e.g., glassmanufacturing process) and/or during shipping or storing of thesubstrates 302 or 303. Typically, the cleaning module 206 uses wetchemical scrubbing and rinsing steps to remove any undesirablecontaminants.

In one example, the process of cleaning the substrate 302 or 303 mayoccur as follows. First, the substrate 302 or 303 enters a contaminantremoval section of the cleaning module 206 from either a transfer tableor an automation device 281. In general, the system controller 290establishes the timing for each substrate 302 or 303 that enters thecleaning module 206. The contaminant removal section may utilize drycylindrical brushes in conjunction with a vacuum system to dislodge andextract contaminants from the surface of the substrate 302. Next, aconveyor within the cleaning module 206 transfers the substrate 302 or303 to a pre-rinse section, where spray tubes dispense hot DI water at atemperature, for example, of 50° C. from a DI water heater onto asurface of the substrate 302 or 303. Commonly, since the devicesubstrate 303 has a TCO layer disposed thereon, and since TCO layers aregenerally electron absorbing materials, DI water is used to avoid anytraces of possible contamination and ionizing of the TCO layer. Next,the rinsed substrate 302, 303 enters a wash section. In the washsection, the substrate 302 or 303 is wet-cleaned with a brush (e.g.,perlon) and hot water. In some cases a detergent (e.g., Alconox™,Citrajet™, Detojet™, Transene™, and Basic H™), surfactant, pH adjustingagent, and other cleaning chemistries are used to clean and removeunwanted contaminants and particles from the substrate surface. A waterre-circulation system recycles the hot water flow. Next, in a finalrinse section of the cleaning module 206, the substrate 302 or 303 isrinsed with water at ambient temperature to remove any traces ofcontaminants. Finally, in a drying section, an air blower is used to drythe substrate 302 or 303 with hot air. In one configuration adeionization bar is used to remove the electrical charge from thesubstrate 302 or 303 at the completion of the drying process.

In the next step, or step 108, separate cells are electrically isolatedfrom one another via scribing processes. Contamination particles on theTCO surface and/or on the bare glass surface can interfere with thescribing procedure. In laser scribing, for example, if the laser beamruns across a particle, it may be unable to scribe a continuous line,and a short circuit between cells will result. In addition, anyparticulate debris present in the scribed pattern and/or on the TCO ofthe cells after scribing can cause shunting and non-uniformities betweenlayers. Therefore, a well-defined and well-maintained process isgenerally needed to ensure that contamination is removed throughout theproduction process. In one embodiment, the cleaning module 206 isavailable from the Energy and Environment Solutions division of AppliedMaterials in Santa Clara, Calif.

Referring to FIGS. 1 and 2, in one embodiment, prior to performing step108 the substrates 302 are transported to a front end processing module(not illustrated in FIG. 2) in which a front contact formation process,or step 107, is performed on the substrate 302. In one embodiment, thefront end processing module is similar to the processing module 218discussed below. In step 107, the one or more substrate front contactformation steps may include one or more preparation, etching and/ormaterial deposition steps that are used to form the front contactregions on a bare solar cell substrate 302. In one embodiment, step 107generally comprises one or more PVD steps that are used to form thefront contact region on a surface of the substrate 302. In oneembodiment, the front contact region contains a transparent conductingoxide (TCO) layer that may contain metal element selected from a groupconsisting of zinc (Zn), aluminum (Al), indium (In), and tin (Sn). Inone example, a zinc oxide (ZnO) is used to form at least a portion ofthe front contact layer. In one embodiment, the front end processingmodule is an ATON™ PVD 5.7 tool available from Applied Materials inSanta Clara, Calif. in which one or more processing steps are performedto deposit the front contact formation steps. In another embodiment, oneor more CVD steps are used to form the front contact region on a surfaceof the substrate 302.

Next the device substrate 303 is transported to the scribe module 208 inwhich step 108, or a front contact isolation step, is performed on thedevice substrate 303 to electrically isolate different regions of thedevice substrate 303 surface from each other. In step 108, material isremoved from the device substrate 303 surface by use of a materialremoval step, such as a laser ablation process. The success criteria forstep 108 are to achieve good cell-to-cell and cell-to-edge isolationwhile minimizing the scribe area. In one embodiment, a Nd:vanadate(Nd:YVO₄) laser source is used ablate material from the device substrate303 surface to form lines that electrically isolate one region of thedevice substrate 303 from the next. In one embodiment, the laser scribeprocess performed during step 108 uses a 1064 nm wavelength pulsed laserto pattern the material disposed on the substrate 302 to isolate each ofthe individual cells (e.g., reference cells 382A and 382B) that make upthe solar cell 300. In one embodiment, a 5.7 m² substrate laser scribemodule available from Applied Materials, Inc. of Santa Clara, Calif. isused to provide simple reliable optics and substrate motion for accurateelectrical isolation of regions of the device substrate 303 surface. Inanother embodiment, a water jet cutting tool or diamond scribe is usedto isolate the various regions on the surface of the device substrate303. In one aspect, it is desirable to assure that the temperature ofthe device substrates 303 entering the scribe module 208 are at atemperature in a range between about 20° C. and about 26° C. by use ofan active temperature control hardware assembly that may contain aresistive heater and/or chiller components (e.g., heat exchanger,thermoelectric device). In one embodiment, it is desirable to controlthe device substrate 303 temperature to about 25+/−0.5° C.

Next the device substrate 303 is transported to the cleaning module 210in which step 110, or a pre-deposition substrate cleaning step, isperformed on the device substrate 303 to remove any contaminants foundon the surface of the device substrate 303 after performing the cellisolation step (step 108). Typically, the cleaning module 210 uses wetchemical scrubbing and rinsing steps to remove any undesirablecontaminants found on the device substrate 303 surface after performingthe cell isolation step. In one embodiment, a cleaning process similarto the processes described in step 106 above is performed on the devicesubstrate 303 to remove any contaminants on the surface(s) of the devicesubstrate 303.

Next, the device substrate 303 is transported to the processing module212 in which step 112, which comprises one or more photoabsorberdeposition steps, is performed on the device substrate 303. In step 112,the one or more photoabsorber deposition steps may include one or morepreparation, etching, and/or material deposition steps that are used toform the various regions of the solar cell device. Step 112 generallycomprises a series of sub-processing steps that are used to form one ormore p-i-n junctions. In one embodiment, the one or more p-i-n junctionscomprise amorphous silicon and/or microcrystalline silicon materials. Ingeneral, the one or more processing steps are performed in one or morecluster tools (e.g., cluster tools 212A-212D) found in the processingmodule 212 to form one or more layers in the solar cell device formed onthe device substrate 303. In one embodiment, the device substrate 303 istransferred to an accumulator 211A prior to being transferred to one ormore of the cluster tools 212A-212D. In one embodiment, in cases wherethe solar cell device is formed to include multiple junctions, such asthe tandem junction solar cell 300 illustrated in FIG. 3B, the clustertool 212A in the processing module 212 is adapted to form the firstp-i-n junction 320 and cluster tools 212B-212D are configured to formthe second p-i-n junction 330. Information regarding the hardware andprocessing methods used to deposit one or more layers in the p-i-njunctions is further described in U.S. patent application Ser. No.12/178,289 [Attorney docket # APPM 11709.P3], filed Jul. 23, 2008, andU.S. patent application Ser. No. 12/170,387 [Attorney docket # APPM11710], filed Jul. 9, 2008, which are both herein incorporated byreference.

In one embodiment of the process sequence 100, a cool down step, or step113, is performed after step 112 has been performed. The cool down stepis generally used to stabilize the temperature of the device substrate303 to assure that the processing conditions seen by each devicesubstrate 303 in the subsequent processing steps are repeatable.Generally, the temperature of the device substrate 303 exiting theprocessing module 212 could vary by many degrees Celsius and exceed atemperature of 50° C., which can cause variability in the subsequentprocessing steps and solar cell performance.

In one embodiment, the cool down step 113 is performed in one or more ofthe substrate supporting positions found in one or more accumulators211. In one configuration of the production line, as shown in FIG. 2,the processed device substrates 303 may be positioned in one of theaccumulators 211B for a desired period of time to control thetemperature of the device substrate 303. In one embodiment, the systemcontroller 290 is used to control the positioning, timing, and movementof the device substrates 303 through the accumulator(s) 211 to controlthe temperature of the device substrates 303 before proceeding downstream through the production line.

Next, the device substrate 303 is transported to the scribe module 214in which step 114, or the interconnect formation step, is performed onthe device substrate 303 to electrically isolate various regions of thedevice substrate 303 surface from each other. In step 114, material isremoved from the device substrate 303 surface by use of a materialremoval step, such as a laser ablation process. In one embodiment, anNd:vanadate (Nd:YVO₄) laser source is used ablate material from thesubstrate surface to form lines that electrically isolate one solar cellfrom the next. In one embodiment, a 5.7 m² substrate laser scribe moduleavailable from Applied Materials, Inc. is used to perform the accuratescribing process. In one embodiment, the laser scribe process performedduring step 108 uses a 532 nm wavelength pulsed laser to pattern thematerial disposed on the device substrate 303 to isolate the individualcells that make up the solar cell 300. As shown in FIG. 3E, in oneembodiment, the trench 381B is formed in the first p-i-n junction 320layers by used of a laser scribing process. In another embodiment, awater jet cutting tool or diamond scribe is used to isolate the variousregions on the surface of the solar cell. In one aspect, it is desirableto assure that the temperature of the device substrates 303 entering thescribe module 214 are at a temperature in a range between about 20° C.and about 26° C. by use of an active temperature control hardwareassembly that may contain a resistive heater and/or chiller components(e.g., heat exchanger, thermoelectric device). In one embodiment, it isdesirable to control the substrate temperature to about 25+/−0.5° C.

In one embodiment, the solar cell production line 200 has at least oneaccumulator 211 positioned after the scribe module(s) 214. Duringproduction accumulators 211C may be used to provide a ready supply ofsubstrates to a contact deposition chamber 218, and/or provide acollection area where substrates coming from the processing module 212can be stored if the contact deposition chamber 218 goes down or can notkeep up with the throughput of the scribe module(s) 214. In oneembodiment it is generally desirable to monitor and/or actively controlthe temperature of the substrates exiting the accumulators 211C toassure that the results of the back contact formation step 120 arerepeatable. In one aspect, it is desirable to assure that thetemperature of the substrates exiting the accumulators 211C or arrivingat the contact deposition chamber 218 are at a temperature in a rangebetween about 20° C. and about 26° C. In one embodiment, it is desirableto control the substrate temperature to about 25+/−0.5° C. In oneembodiment, it is desirable to position one or more accumulators 211Cthat are able to retain at least about 80 substrates.

Next, the device substrate 303 is transported to the processing module218 in which one or more substrate back contact formation steps, or step118, are performed on the device substrate 303. In step 118, the one ormore substrate back contact formation steps may include one or morepreparation, etching, and/or material deposition steps that are used toform the back contact regions of the solar cell device. In oneembodiment, step 118 generally comprises one or more PVD steps that areused to form the back contact layer 350 on the surface of the devicesubstrate 303. In one embodiment, the one or more PVD steps are used toform a back contact region that contains a metal layer selected from agroup consisting of zinc (Zn), tin (Sn), aluminum (Al), copper (Cu),silver (Ag), nickel (Ni), and vanadium (V). In one example, a zinc oxide(ZnO) or nickel vanadium alloy (NiV) is used to form at least a portionof the back contact layer 305. In one embodiment, the one or moreprocessing steps are performed using an ATON™ PVD 5.7 tool availablefrom Applied Materials in Santa Clara, Calif. In another embodiment, oneor more CVD steps are used to form the back contact layer 350 on thesurface of the device substrate 303.

In one embodiment, the solar cell production line 200 has at least oneaccumulator 211 positioned after the processing module 218. Duringproduction, the accumulators 211D may be used to provide a ready supplyof substrates to the scribe modules 220, and/or provide a collectionarea where substrates coming from the processing module 218 can bestored if the scribe modules 220 go down or can not keep up with thethroughput of the processing module 218. In one embodiment it isgenerally desirable to monitor and/or actively control the temperatureof the substrates exiting the accumulators 211D to assure that theresults of the back contact formation step 120 are repeatable. In oneaspect, it is desirable to assure that the temperature of the substratesexiting the accumulators 211D or arriving at the scribe module 220 areat a temperature in a range between about 20° C. and about 26° C. In oneembodiment, it is desirable to control the substrate temperature toabout 25+/−0.5° C. In one embodiment, it is desirable to position one ormore accumulators 211C that are able to retain at least about 80substrates.

Next, the device substrate 303 is transported to the scribe module 220in which step 120, or a back contact isolation step, is performed on thedevice substrate 303 to electrically isolate the plurality of solarcells contained on the substrate surface from each other. In step 120,material is removed from the substrate surface by use of a materialremoval step, such as a laser ablation process. In one embodiment, aNd:vanadate (Nd:YVO₄) laser source is used ablate material from thedevice substrate 303 surface to form lines that electrically isolate onesolar cell from the next. In one embodiment, a 5.7 m² substrate laserscribe module, available from Applied Materials, Inc., is used toaccurately scribe the desired regions of the device substrate 303. Inone embodiment, the laser scribe process performed during step 120 usesa 532 nm wavelength pulsed laser to pattern the material disposed on thedevice substrate 303 to isolate the individual cells that make up thesolar cell 300. As shown in FIG. 3E, in one embodiment, the trench 381Cis formed in the first p-i-n junction 320 and back contact layer 350 byuse of a laser scribing process. In one aspect, it is desirable toassure that the temperature of the device substrates 303 entering thescribe module 220 are at a temperature in a range between about 20° C.and about 26° C. by use of an active temperature control hardwareassembly that may contain a resistive heater and/or chiller components(e.g., heat exchanger, thermoelectric device). In one embodiment, it isdesirable to control the substrate temperature to about 25+/−0.5° C.

Next, the device substrate 303 is transported to the quality assurancemodule 222 in which step 122, or quality assurance and/or shunt removalsteps, are performed on the device substrate 303 to assure that thedevices formed on the substrate surface meet a desired quality standardand in some cases correct defects in the formed device. In step 122, aprobing device is used to measure the quality and material properties ofthe formed solar cell device by use of one or more substrate contactingprobes. In one embodiment, the quality assurance module 222 projects alow level of light at the p-i-n junction(s) of the solar cell and usesthe one more probes to measure the output of the cell to determine theelectrical characteristics of the formed solar cell device(s). If themodule detects a defect in the formed device, it can take correctiveactions to fix the defects in the formed solar cells on the devicesubstrate 303. In one embodiment, if a short or other similar defect isfound, it may be desirable to create a reverse bias between regions onthe substrate surface to control and or correct one or more of thedefectively formed regions of the solar cell device. During thecorrection process the reverse bias generally delivers a voltage highenough to cause the defects in the solar cells to be corrected. In oneexample, if a short is found between supposedly isolated regions of thedevice substrate 303 the magnitude of the reverse bias may be raised toa level that causes the conductive elements in areas between theisolated regions to change phase, decompose, or become altered in someway to eliminate or reduce the magnitude of the electrical short. In oneembodiment of the process sequence 100, the quality assurance module 222and factory automation system are used together to resolve qualityissues found in a formed device substrate 303 during the qualityassurance testing. In one case, a device substrate 303 may be sent backupstream in the processing sequence to allow one or more of thefabrication steps to be re-performed on the device substrate 303 (e.g.,back contact isolation step (step 120)) to correct one or more qualityissues with the processed device substrate 303.

Next, the device substrate 303 is optionally transported to thesubstrate sectioning module 224 in which a substrate sectioning step 124is used to cut the device substrate 303 into a plurality of smallerdevice substrates 303 to form a plurality of smaller solar cell devices.In one embodiment of step 124, the device substrate 303 is inserted intosubstrate sectioning module 224 that uses a CNC glass cutting tool toaccurately cut and section the device substrate 303 to form solar celldevices that are a desired size. In one embodiment, the device substrate303 is inserted into the cutting module 224 that uses a glass scribingtool to accurately score the surface of the device substrate 303. Thedevice substrate 303 is then broken along the scored lines to producethe desired size and number of sections needed for the completion of thesolar cell devices.

In one embodiment, the solar cell production line 200 is adapted toaccept (step 102) and process substrate 302 or device substrates 303that are 5.7 m² or larger. In one embodiment, these large areasubstrates 302 are partially processed and then sectioned into four 1.4m² device substrates 303 during step 124. In one embodiment, the systemis designed to process large device substrates 303 (e.g., TCO coated2200 mm×2600 mm×3 mm glass) and produce various sized solar cell deviceswithout additional equipment or processing steps. Currently amorphoussilicon (a-Si) thin film factories must have one product line for eachdifferent size solar cell device. In the present invention, themanufacturing line is able to quickly switch to manufacture differentsolar cell device sizes. In one aspect of the invention, themanufacturing line is able to provide a high solar cell devicethroughput, which is typically measured in Mega-Watts per year, byforming solar cell devices on a single large substrate and thensectioning the substrate to form solar cells of a more preferable size.

In one embodiment of the production line 200, the front end of the line(FEOL) (e.g., steps 102-122) is designed to process a large area devicesubstrate 303 (e.g., 2200 mm×2600 mm), and the back end of the line(BEOL) is designed to further process the large area device substrate303 or multiple smaller device substrates 303 formed by use of thesectioning process. In this configuration, the remainder of themanufacturing line accepts and further processes the various sizes. Theflexibility in output with a single input is unique in the solar thinfilm industry and offers significant savings in capital expenditure. Thematerial cost for the input glass is also lower since solar cell devicemanufacturers can purchase a larger quantity of a single glass size toproduce the various size modules.

In one embodiment, steps 102-122 can be configured to use equipment thatis adapted to perform process steps on large device substrates 303, suchas 2200 mm×2600 mm×3 mm glass device substrates 303, and steps 124onward can be adapted to fabricate various smaller sized solar celldevices with no additional equipment required. In another embodiment,step 124 is positioned in the process sequence 200 prior to step 122 sothat the initially large device substrate 303 can be sectioned to formmultiple individual solar cells that are then tested and characterizedone at a time or as a group (i.e., two or more at a time). In this case,steps 102-121 are configured to use equipment that is adapted to performprocess steps on large device substrates 303, such as 2200 mm×2600 mm×3mm glass substrates, and steps 124 and 122 onward are adapted tofabricate various smaller sized modules with no additional equipmentrequired. A more detailed description of an exemplary substratesectioning module 224 is presented below in the section entitled,“Substrate Sectioning Module and Processes.”

Referring back to FIGS. 1 and 2, the device substrate 303 is nexttransported to the seamer/edge deletion module 226 in which a substratesurface and edge preparation step 126 is used to prepare varioussurfaces of the device substrate 303 to prevent yield issues later on inthe process. In one embodiment of step 126, the device substrate 303 isinserted into seamer/edge deletion module 226 to prepare the edges ofthe device substrate 303 to shape and prepare the edges of the devicesubstrate 303. Damage to the device substrate 303 edge can affect thedevice yield and the cost to produce a usable solar cell device. Inanother embodiment, the seamer/edge deletion module 226 is used toremove deposited material from the edge of the device substrate 303(e.g., 10 mm) to provide a region that can be used to form a reliableseal between the device substrate 303 and the backside glass (i.e.,steps 134-136 discussed below). Material removal from the edge of thedevice substrate 303 may also be useful to prevent electrical shorts inthe final formed solar cell.

In one embodiment, a diamond impregnated belt is used to grind thedeposited material from the edge regions of the device substrate 303. Inanother embodiment, a grinding wheel is used to grind the depositedmaterial from the edge regions of the device substrate 303. In anotherembodiment, dual grinding wheels are used to remove the depositedmaterial from the edge of the device substrate 303. In yet anotherembodiment, grit blasting or laser ablation techniques are used toremove the deposited material from the edge of the device substrate 303.In one aspect, the seamer/edge deletion module 226 is used to round orbevel the edges of the device substrate 303 by use of shaped grindingwheels, angled and aligned belt sanders, and/or abrasive wheels.

Next the device substrate 303 is transported to the pre-screen module228 in which optional pre-screen steps 128 are performed on the devicesubstrate 303 to assure that the devices formed on the substrate surfacemeet a desired quality standard. In step 128, a light emitting sourceand probing device are used to measure the output of the formed solarcell device by use of one or more substrate contacting probes. If themodule 228 detects a defect in the formed device it can take correctiveactions or the solar cell can be scrapped.

Next the device substrate 303 is transported to the cleaning module 230in which step 130, or a pre-lamination substrate cleaning step, isperformed on the device substrate 303 to remove any contaminants foundon the surface of the substrates 303 after performing steps 122-128.Typically, the cleaning module 230 uses wet chemical scrubbing andrinsing steps to remove any undesirable contaminants found on thesubstrate surface after performing the cell isolation step. In oneembodiment, a cleaning process similar to the processes described instep 106 is performed on the substrate 303 to remove any contaminants onthe surface(s) of the substrate 303.

Next the substrate 303 is transported to a bonding wire attach module231 in which step 131, or a bonding wire attach step, is performed onthe substrate 303. Step 131 is used to attach the various wires/leadsrequired to connect the various external electrical components to theformed solar cell device. Typically, the bonding wire attach module 231is an automated wire bonding tool that is advantageously used toreliably and quickly form the numerous interconnects that are oftenrequired to form the large solar cells formed in the production line200. In one embodiment, the bonding wire attach module 231 is used toform the side-buss 355 (FIG. 3C) and cross-buss 356 on the formed backcontact region (step 118). In this configuration the side-buss 355 maybe a conductive material that can be affixed, bonded, and/or fused tothe back contact layer 350 found in the back contact region to form agood electrical contact. In one embodiment, the side-buss 355 andcross-buss 356 each comprise a metal strip, such as copper tape, anickel coated silver ribbon, a silver coated nickel ribbon, a tin coatedcopper ribbon, a nickel coated copper ribbon, or other conductivematerial that can carry the current delivered by the solar cell and bereliably bonded to the metal layer in the back contact region. In oneembodiment, the metal strip is between about 2 mm and about 10 mm wideand between about 1 mm and about 3 mm thick. The cross-buss 356, whichis electrically connected to the side-buss 355 at the junctions, can beelectrically isolated from the back contact layer(s) of the solar cellby use of an insulating material 357, such as an insulating tape. Theends of each of the cross-busses 356 generally have one or more leadsthat are used to connect the side-buss 355 and the cross-buss 356 to theelectrical connections found in a junction box 370, which is used toconnect the formed solar cell to the other external electricalcomponents. Further information on soldering bus wire to thin film solarmodules is disclosed in U.S. Provisional Patent Application Ser. No.60/967,077, U.S. Provisional Patent Application Ser. No. 61/023,810, andU.S. Provisional Patent Application Ser. No. 61/032,005, which areincorporated by reference herein.

In the next step, step 132, a bonding material 360 (FIG. 3D) and “backglass” substrate 361 are prepared for delivery into the solar cellformation process (i.e., process sequence 100). The preparation processis generally performed in the glass lay-up module 232, which generallycomprises a material preparation module 232A, a glass loading module232B and a glass cleaning module 232C. The back glass substrate 361 isbonded onto the device substrate 303 formed in steps 102-130 above byuse of a laminating process (step 134 discussed below). In general, step132 requires the preparation of a polymeric material that is to beplaced between the back glass substrate 361 and the deposited layers onthe device substrate 303 to form a hermetic seal to prevent theenvironment from attacking the solar cell during its life. Referring toFIG. 2, step 132 generally comprises a series of sub-steps in which abonding material 360 is prepared in the material preparation module232A, the bonding material 360 is then placed over the device substrate303, the back glass substrate 361 is loaded into the loading module 232Band is washed by use of the cleaning module 232C, and the back glasssubstrate 361 is placed over the bonding material 360 and the devicesubstrate 303.

In one embodiment, the material preparation module 232A is adapted toreceive the bonding material 360 in a sheet form and perform one or morecutting operations to provide a bonding material, such as PolyvinylButyral (PVB) or Ethylene Vinyl Acetate (EVA) that is sized to form areliable seal between the backside glass and the solar cells formed onthe device substrate 303. In general, when using bonding materials 360that are polymeric, it is desirable to control the temperature (e.g.,16-18° C.) and relative humidity (e.g., RH 20-22%) of the solar cellproduction line 200 where the bonding material 360 is stored andintegrated into the solar cell device to assure that the attributes ofthe bond formed in the bonding module 234 are repeatable and thedimensions of the polymeric material is stable. It is generallydesirable to store the bonding material prior to use in temperature andhumidity controlled area (e.g., T=6-8° C.; RH=20-22%). The tolerancestack up of the various components in the bonded device (Step 134) canbe an issue when forming large solar cells, therefore accurate controlof the bonding material properties and tolerances of the cutting processare required to assure that a reliable hermetic seal is formed. In oneembodiment, PVB may be used to advantage due to its UV stability,moisture resistance, thermal cycling, good US fire rating, compliancewith Intl Building Code, low cost, and reworkable thermo-plasticproperties. In one part of step 132, the bonding material 360 istransported and positioned over the back contact layer 350, theside-buss 355 (FIG. 3C), and the cross-buss 356 (FIG. 3C) elements ofthe device substrate 303 using an automated robotic device. The devicesubstrate 303 and bonding material 360 are then positioned to receive aback glass substrate 361, which can be placed thereon by use of the sameautomated robotic device used to position the bonding material 360, or asecond automated robotic device.

In one embodiment, prior to positioning the back glass substrate 361over the bonding material 360, one or more preparation steps areperformed to the back glass substrate 361 to assure that subsequentsealing processes and final solar product are desirably formed. In onecase, the back glass substrate 361 is received in a “raw” state wherethe edges, overall size, and/or cleanliness of the substrate 361 are notwell controlled. Receiving “raw” substrates reduces the cost to prepareand store substrates prior to forming a solar device and thus reducesthe solar cell device cost, facilities costs, and production costs ofthe finally formed solar cell device. In one embodiment of step 132, theback glass substrate 361 surfaces and edges are prepared in a seamingmodule (e.g., seamer 204) prior to performing the back glass substratecleaning step. In the next sub-step of step 232 the back glass substrate361 is transported to the cleaning module 232B in which a substratecleaning step, is performed on the substrate 361 to remove anycontaminants found on the surface of the substrate 361. Commoncontaminants may include materials deposited on the substrate 361 duringthe substrate forming process (e.g., glass manufacturing process) and/orduring shipping of the substrates 361. Typically, the cleaning module232B uses wet chemical scrubbing and rinsing steps to remove anyundesirable contaminants as discussed above. The prepared back glasssubstrate 361 is then positioned over the bonding material and partiallydevice substrate 303 by use of an automated robotic device.

Next the device substrate 303, the back glass substrate 361, and thebonding material 360 are transported to the bonding module 234 in whichstep 134, or lamination steps are performed to bond the backside glasssubstrate 361 to the device substrate formed in steps 102-130 discussedabove. In step 134, a bonding material 360, such as Polyvinyl Butyral(PVB) or Ethylene Vinyl Acetate (EVA), is sandwiched between thebackside glass substrate 361 and the device substrate 303. Heat andpressure are applied to the structure to form a bonded and sealed deviceusing various heating elements and other devices found in the bondingmodule 234. The device substrate 303, the back glass substrate 361 andbonding material 360 thus form a composite solar cell structure 304(FIG. 3D) that at least partially encapsulates the active regions of thesolar cell device. In one embodiment, at least one hole formed in theback glass substrate 361 remains at least partially uncovered by thebonding material 360 to allow portions of the cross-buss 356 or the sidebuss 355 to remain exposed so that electrical connections can be made tothese regions of the solar cell structure 304 in future steps (i.e.,step 138).

Next the composite solar cell structure 304 is transported to theautoclave module 236 in which step 136, or autoclave steps are performedon the composite solar cell structure 304 to remove trapped gasses inthe bonded structure and assure that a good bond is formed during step134. In step 134, a bonded solar cell structure 304 is inserted in theprocessing region of the autoclave module where heat and high pressuregases are delivered to reduce the amount of trapped gas and improve theproperties of the bond between the device substrate 303, back glasssubstrate, and bonding material 360. The processes performed in theautoclave are also useful to assure that the stress in the glass andbonding layer (e.g., PVB layer) are more controlled to prevent futurefailures of the hermetic seal or failure of the glass due to the stressinduced during the bonding/lamination process. In one embodiment, it maybe desirable to heat the device substrate 303, back glass substrate 361,and bonding material 360 to a temperature that causes stress relaxationin one or more of the components in the formed solar cell structure 304.

Next the solar cell structure 304 is transported to the junction boxattachment module 238 in which junction box attachment steps 138 areperformed on the formed solar cell structure 304. The junction boxattachment module 238, used during step 138, is used to install ajunction box 370 (FIG. 3C) on a partially formed solar cell. Theinstalled junction box 370 acts as an interface between the externalelectrical components that will connect to the formed solar cell, suchas other solar cells or a power grid, and the internal electricalconnections points, such as the leads, formed during step 131. In oneembodiment, the junction box 370 contains one or more connection points371, 372 so that the formed solar cell can be easily and systematicallyconnected to other external devices to deliver the generated electricalpower.

Next the solar cell structure 304 is transported to the device testingmodule 240 in which device screening and analysis steps 140 areperformed on the solar cell structure 304 to assure that the devicesformed on the solar cell structure 304 surface meet desired qualitystandards. In one embodiment, the device testing module 240 is a solarsimulator module that is used to qualify and test the output of the oneor more formed solar cells. In step 140, a light emitting source andprobing device are used to measure the output of the formed solar celldevice by use of one or more automated components that are adapted tomake electrical contact with terminals in the junction box 370. If themodule detects a defect in the formed device it can take correctiveactions or the solar cell can be scrapped.

Next the solar cell structure 304 is transported to the supportstructure module 241 in which support structure mounting steps 141 areperformed on the solar cell structure 304 to provide a complete solarcell device that has one or more mounting elements attached to the solarcell structure 304 formed using steps 102-140 to a complete solar celldevice that can easily be mounted and rapidly installed at a customer'ssite.

Next the solar cell structure 304 is transported to the unload module242 in which step 142, or device unload steps are performed on thesubstrate to remove the formed solar cells from the solar cellproduction line 200.

In one embodiment of the solar cell production line 200, one or moreregions in the production line are positioned in a clean roomenvironment to reduce or prevent contamination from affecting the solarcell device yield and useable lifetime. In one embodiment, as shown inFIG. 2, a class 10,000 clean room space 250 is placed around the modulesused to perform steps 108-118 and steps 130-134.

Substrate Sectioning Module and Processes

The substrate sectioning module 224 and processing sequence performedduring the substrate sectioning step 124 are used to section a large,partially processed device substrate 303 (i.e., a substrate having oneor more thin silicon films deposited thereon) into two or more devicesubstrates 303 for further processing into a solar module. In oneembodiment, the substrate sectioning module receives a 2600 mm×2200 mmdevice substrate 303 and sections it into two 1300 mm×2200 mm devicesubstrates 303 for further processing. In one embodiment, the substratesectioning module receives a 2600 mm×2200 mm device substrate 303 andsections it into two 2600 mm×1100 mm device substrates 303 for furtherprocessing. In one embodiment, the substrate sectioning module receivesa 2600 mm×2200 mm device substrate 303 and sections it into four 1300mm×1100 mm device substrates 303 for further processing.

In one embodiment, the system controller 290 (FIG. 2) controls thenumber and size of the sections of the device substrates 303 produced bythe substrate sectioning module 224. Accordingly, the system controller290 sends commands to all downstream processes in the sequence 100(FIG. 1) for coordinating both the processes and adjustments to thedownstream modules to accommodate and further process sections of thedevice substrate 303 produced by the substrate sectioning moduleregardless of the size of the sections produced.

FIGS. 4A-4E are top plan, schematic views illustrating a sequence ofsectioning a device substrate 303 according to one embodiment of thesubstrate sectioning module 224. Referring to FIG. 4A, an inlet conveyor410 transports the device substrate 303 into a scribing station 420. Inone embodiment, the side of the device substrate 303 having thin filmsdeposited thereover is facing upward. A scribing conveyor 422 positionsthe device substrate in the scribing station 420 for scribing. In thescribing station 420, as shown in FIG. 4B, a pattern is scribed on theupper surface of the device substrate 303 via a scribing mechanism 424according to the programmed sectioning of the device substrate 303. Inone embodiment, the inlet conveyor 410, the scribing conveyor 422, andthe scribing mechanism 424 are controlled and coordinated with eachother as well as other operations in the sequence 100 (FIG. 1) via thesystem controller 290 (FIG. 2).

In one embodiment, the scribing mechanism 424 is a mechanical scribingmechanism, such as a mechanical scribing wheel. In one embodiment, thescribing mechanism 424 is an optical scribing mechanism, such a laserscribing mechanism. Regardless of the type of scribing mechanism 424employed, it should be noted that the scribing mechanism must cutcompletely through any films deposited on the processing surface of thedevice substrate 303 and cleanly score the upper surface of theunderlying glass.

The scored device substrate 303 is then transported via the scribingstation conveyor 422 partially onto a cross transfer station 430 asshown in FIG. 4C. A first transfer station conveyor 432 is coordinatedwith the scribing station conveyor 422 via the system controller 290 toproperly position the device substrate 303. FIGS. 5A-5C schematicallyillustrate a process for breaking the scored device substrate 303according to one embodiment of the present invention. Referring to FIGS.4C and 5A, the scored device substrate 303 is positioned over a roller426 such that a line scribed along the X-axis is located directly abovethe roller 426. The roller 426 is then raised and placed in contact withthe lower surface of the device substrate 303 as schematically shown inFIG. 5B. As schematically depicted in FIG. 5C, the roller 426 is raisedexerting a lifting force on the lower surface of the device substrate303 along the scribed line and perpendicular to the plane of the devicesubstrate 303 resulting in a clean break along the scribed line.

In one embodiment, the roller 426 is a padded cylindrical rollerextending the length of the device substrate 303. The roller 426 israised by an actuator 428.

In one embodiment, the actuator 428 may be an electric, hydraulic, orpneumatic motor. In one embodiment, the actuator 428 may be a hydraulicor pneumatic cylinder. In one embodiment, the actuator 428 is controlledand coordinated by the system controller 290.

Next, shown in FIG. 4D, a first section 303A of the substrate device 303is fully loaded into the cross transfer station 430 via the firsttransfer conveyor 432. Next, a second transfer conveyor 434, inconjunction with an exit conveyor 440, transfers the first section 303Apartially onto the exit conveyor 440 as shown in FIG. 4E. The secondtransfer station conveyor 434 is coordinated with the exit conveyor 440via the system controller 290 to properly position the device substratesection 303A. Referring to FIGS. 4E and 5A, the scored sectioned devicesubstrate 303A is positioned over the roller 426 such that a linescribed along the Y-axis is located directly above the roller 426. Theroller 426 is then raised and placed in contact with the lower surfaceof the sectioned device substrate 303A as schematically shown in FIG.5B. As schematically depicted in FIG. 5C, the roller 426 is raised toexert a lifting force on the lower surface of the device substratesection 303A along the scribed line and perpendicular to the plane ofthe device substrate section 303A resulting in a clean break along thescribed line. As a result the substrate section 303A is sectioned intotwo smaller device substrate sections 303C and 303D. Each of thesubstrate sections 303C and 303D are then transferred via the secondtransfer conveyor 434 and the exit conveyor 440 into a subsequent modulefor further processing. The above processes are then repeated for thedevice substrate section 303B.

Although the above-described embodiment illustrates processes andapparatus for sectioning a single substrate device 303 into four smallersections, it should be evident that the embodiment works equally wellfor sectioning a single substrate device 303 into two smaller sectionsby adjusting the scribing mechanism 424 to scribe only a single line oneither the X-axis or the Y-axis and performing only a single breakprocess.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A module for sectioning a solar cell device, comprising: an inletconveyor configured to receive commands from a system controller andtransfer a solar cell device into a scribing station of the module; ascribing mechanism configured to receive commands from the systemcontroller and scribe a pattern into a first surface of the solar celldevice; a first positioning mechanism configured to receive commandsfrom the system controller and accurately position the scribed solarcell device over a first break mechanism; and a first actuatorconfigured to receive commands from the system controller and raise thefirst break mechanism.
 2. The module of claim 1, further comprising: across transfer station having a conveyor and a second positioningmechanism, wherein the conveyor is positioned to receive a section ofthe solar cell device from the first positioning mechanism, and whereinthe second positioning mechanism is configured to receive commands fromthe system controller and accurately position the section of the solarcell device over a second break mechanism; a second actuator configuredto receive commands from the system controller and raise the secondbreak mechanism; and an exit conveyor positioned to receive a portion ofthe section of the solar cell device.
 3. The module of claim 2, whereinthe first and second break mechanisms are elongated rollers.
 4. Themodule of claim 3, wherein the first break mechanism extends along afirst axis and the second break mechanism extends along a second axis,and wherein the first and second axes are substantially perpendicular toone another.
 5. The module of claim 1, wherein the scribing mechanism isa mechanical scribing wheel.
 6. The module of claim 1, wherein thescribing mechanism is a laser scribing device.
 7. A method forsectioning a partially processed solar cell device, comprising:receiving a substrate having a processing surface; forming a siliconlayer on the processing surface; sectioning the substrate into a firstand a second section after forming the silicon layer on the processingsurface; and transferring the first section into a next station forfurther processing.
 8. The method of claim 7, wherein sectioning thesubstrate comprises: scribing a first line into a surface of thesubstrate after forming the silicon layer on the processing surface; andactuating a break mechanism to break the substrate along the first line.9. The method of claim 8, wherein the scribing a first line comprisesscribing a line completely through the silicon layer and into theprocessing surface.
 10. The method of claim 8, further comprisingscribing a second line into the processing surface, wherein the secondline is substantially perpendicular to the first line.
 11. The method ofclaim 10, further comprising positioning the first section of thesubstrate adjacent a second break mechanism such that the second scribedline is substantially in line with an axis of the second breakmechanism.
 12. The method of claim 11, further comprising actuating thesecond break mechanism to break the first section along the secondscribed line.
 13. The method of claim 11, wherein the processing surfacehas a surface area greater than about 1.4 m².
 14. A system forfabricating solar cell devices, comprising: a substrate receiving modulethat is adapted to receive a substrate; a cluster tool having aprocessing chamber that is adapted to deposit a silicon-containing layeron a surface of the substrate; a back contact deposition chamberconfigured to deposit a back contact layer on a surface of thesubstrate; a substrate sectioning module configured to section thesubstrate into two or more sections; and a system controller forcontrolling and coordinating functions of each of the substratereceiving module, the cluster tool, the processing chamber, the backcontact deposition chamber, and the substrate sectioning module.
 15. Thesystem of claim 14, wherein the substrate sectioning module comprises aCNC glass cutter.
 16. The system of claim 14, wherein the substratesectioning module comprises a scribing station configured to scribe aline into a surface of the substrate, a breaking station configured tobreak the substrate along the line, and a positioning mechanism forpositioning the substrate such that the line scribed into the substrateis substantially aligned with the breaking mechanism.
 17. The system ofclaim 16, wherein the substrate sectioning module further comprises asecond positioning mechanism for positioning one of the sections of thesubstrate adjacent a second breaking mechanism, such that the secondbreaking mechanism is substantially aligned with a second line scribedinto the substrate.
 18. A method of processing a solar cell device,comprising: cleaning a substrate to remove one or more contaminants froma surface of the substrate; depositing a photoabsorbing layer on thesurface of the substrate; removing at least a portion of thephotoabsorbing layer from a region on the surface of the substrate;depositing a back contact layer on the surface of the substrate;sectioning the substrate into two or more sections; performing an edgedeletion process on a surface of one of the sections; bonding a backglass substrate to the surface of one of the sections to form acomposite structure; and attaching a junction box to the compositestructure.
 19. The method of claim 18, wherein the sectioning thesubstrate comprises cutting the substrate with a CNC glass cutter. 19.The method of claim 18, wherein sectioning the substrate comprisesscribing a first line into the substrate, aligning the first line with afirst break mechanism, and breaking the substrate along the first line.20. The method of claim 19, wherein sectioning the substrate furthercomprises scribing a second line into the substrate, aligning the secondline with a second break mechanism, and breaking the substrate along thesecond line, wherein the first line is substantially perpendicular tothe second line.